We don’t have a way built into the hardware of Circuit 4 to control the volume of the piezo. In this project, we explore an approach to controlling its volume through software (i.e., the sketch that controls the piezo). When we set the piezo voltage to HIGH, it changes shape. This causes a pulse of air to move out of it. We then switch the voltage from HIGH to LOW to prepare for the next pulse. If we switch the voltage back to low sooner, we might be able to make soften the pulse. This could reduce the volume without changing the frequency. In this project, we change how long the piezo voltage is either HIGH or LOW to create a sound that’s like a mosquito buzzing around your head.

Let’s look first at the piezoTone function. We changed it for this project by adding an extra argument, partOn. void piezoTone(long freq, long duration, long partOn){ In the past, we calculate the amount of time that needs to elapse between pulses to create a certain frequency. Now, we use ­isOn to set how long the piezo voltage remains HIGH and then set it LOW for the remainder of period: digitalWrite(piezo,HIGH); delayMicroseconds(partOn); digitalWrite(piezo,LOW); delayMicroseconds(period - partOn); Back to the setup() block. We set the speed that the mosquito approaches by setting buzzAway to a random value between 25 and 100 milliseconds. The variable level is the number of microseconds that the piezo is HIGH during each pulse. We use a for loop to increment this value for 1 to 50. Through trial and error, we found that the piezo reaches full volume by the time level reaches 50 microseconds: buzzAway = random(25,100); for(level = 1; level < 50; level++){ piezoTone(1047,buzzAway,level); } Next, we repeat this code, but reset the speed of buzzAway and increment level from 50 to 1 to simulate the mosquito buzzing away from our ear: buzzAway = random(25,100); for(level = 50; level > 1; level--){ piezoTone(1047,buzzAway,level); } And that’s it!